1. Field of the Invention
The present invention relates to a bag conveying apparatus used in a bag filling packaging machine in which bags (with the bag mouths facing upward) with both edges thereof being gripped by grippers are conveyed continuously or intermittently along an annular path.
2. Prior Art
In a typical bag filling packaging machine, both edges of bags are gripped by gripper pairs, and such bags are conveyed continuously or intermittently along an annular path and respective packaging treatments such as opening, filling with contents and sealing, etc. are successively performed on the bags.
One type of bag conveying apparatus used in such a bag filling packaging machine includes a plurality of sprockets (driving sprocket(s) and driven sprocket(s)) and an endless chain. Sprockets are disposed in specified positions on a horizontal plane, and the endless chain is provided between the sprockets. The endless chain has a plurality of gripper pairs that are installed at equal intervals so as to grip the bags. The driving sprocket(s) are continuously or intermittently rotated, and the bags gripped by the gripper pairs are continuously or intermittently conveyed along a predetermined annular path.
In the bag conveying apparatus described in Japanese Patent Application Laid-Open (Kokai) No. S59-221201, two sprockets are installed, and an endless chain is provided between these sprockets. In the bag conveying apparatus disclosed in Japanese Patent Application Publication (Kokoku) No. S56-48363, an endless chain is provided between four sprockets.
The conveying apparatus with two sprockets has a simpler structure than four-sprocket conveying apparatuses and has a better cleaning and maintenance characteristics. Also, it can keep the cost low.
However, in either type, a driven sprocket(s) must be provided for mounting the endless chain, and further simplification of the structure and reduction of the cost are not considered feasible.
Meanwhile, various packaging devices are disposed in a bag filling packaging machine. In order to make the bag filling packaging machine as a whole more compact, it is desirable that most of these devices be installed in upright positions inside the track of the endless chain. However, even inside the track, space cannot be found for the upright installation of the packaging treatment devices in the sprocket installation areas and surrounding areas (because of the need to prevent interference with the rotating sprockets). Accordingly, a corresponding amount of space is required on the outside of the track, and thus further reduction in the size of the bag filling packaging machine is hindered.
Furthermore, the weight of the gripper pairs, the weight of the filled bags and the impact during filling are loaded on the endless chain of the bag conveying apparatus. Accordingly, in order to withstand these weights and impacts, and in order to allow a secure and stable packaging processing, it is necessary that the gripper pairs be operated stably and with good precision over a long period of time. However, this requirement has not been sufficiently satisfied by conventional bag conveying apparatuses (especially chain type apparatuses that are mainly commercially marketed devices). As a result, such bag conveying apparatuses require frequent maintenance and parts replacement.
Accordingly, the present invention is to solve the problems with the prior art bag conveying apparatus; and it is an object of the present invention to provide a simple and low cost bag conveying apparatus that can reduce the size of bag filling packaging machines.
It is another object of the present invention to provide a bag conveying apparatus for packaging process machines in which the gripper pairs that hold bags are rotated in a stable fashion and with good precision over a long period of time.
The above objects are accomplished by a unique structure for a bag conveying apparatus used in a bag filling packaging machine, wherein the bag conveying apparatus is comprised of:
a sprocket connected to a driving means and rotated continuously or intermittently on a horizontal plane,
a fixed guide member which has a guide section that has a substantially semicircular shape when viewed from above, the fixed guide member being disposed on substantially the same horizontal plane as the sprocket with a specified spacing in between, and
an endless chain provided between the sprocket and the guide section of the fixed guide member, and
a plurality of gripper pairs installed at equal intervals on the endless chain, the plurality of gripper pairs being for griping both edges of a bag.
In this structure, the sprocket is provided at a predetermined position, and the guide section of the fixed guide member is provided so as to be movable toward and away from said sprocket (in a horizontal direction) and is constantly urged in a direction opposite from the sprocket.
Furthermore, in the present invention, the endless chain is comprised of a plurality of links that are connected via connecting shafts; guide rollers which are rotatable about their own vertical axes are disposed on each one of the connecting shafts; an inside guide roller which is rotatable about its own horizontal axis is disposed on an inside of each one of the links; and the guide section of the fixed guide member is provided with a roller guide section and a guide groove, so that the guide rollers of the endless chain contact the roller guide, and the inside guide roller of the endless chain fits in the guide groove.
In addition, the sprocket is provided on an outer circumferential surface thereof with recessed portions at equal intervals, so that the guide rollers of the endless chain engage with the recessed portions; and the sprocket is further provided with a supporting groove, so that the inside guide roller of the endless chain fits in the supporting groove.
The above objects are accomplished also by a unique structure for a gripper endless chain that comprises a plurality of links connected via connecting shafts in an endless configuration, and a plurality of gripper pairs that grip both edges of a bag are disposed at equal intervals on the chain; and in this gripper chain, upper and lower rollers are disposed respectively on and under each of the connecting shafts so that the rollers are rotatable about their own vertical axes; and an inside roller is disposed on an inside of each of the links so that the inside roller is rotatable about its own horizontal axis.
In this structure, at least one of the plurality of gripper pairs is provided on each one of the links; and each of the links is formed with covering portions on both ends of an outer circumferential side thereof so as to cover the connecting portions of each one of the links.